The invention relates to copy sheet control and, more particularly, to the capability of adjusting jam detection timing windows for selected sensors.
If imaging machines are to become more versatile in completing complex jobs, the machine control must be able to adapt to a wide variety of requirements, particularly timing requirements in an efficient manner. Normal timing deviations in a machine should not result in the declaration of an unnecessary timing fault.
Currently, in most reprographic machines a nominal preset reference is specified for paper path timing and jam detection windows. This means that all variables such as paper path geometries, paper weight, component response, speed variation and life degradation have to be accommodated with a single preset jam detection window.
U.S. Pat. No. 4,804,998 discloses a control method for deciding whether or not the transport of a sheet in a copier is normal. Sheet feed sensors, a registration sensor, a separation sensor, a fixation sensor, a discharge sensor and other sensors responsive to the ends of a sheet are provided. The actual timing of passage of a sheet sensed by one of the sensors is compared with reference timing, and the resulting increment or decrement in timing is fed back to the reference timings which are respectively, assigned to each of the other sensors that are located downstream of that one sensor. This prevents the deviation in timing from being sequentially accumulated from the upstream sensor to the downstream sensor. When the sum of the increments and decrements exceeds a predetermined value, an alarm is produced for alerting a person to such an occurrence.
A difficulty, however, with the system described in the '998 patent is that accommodations for timing deviations of a first sensor are passed on to sensors downstream, but no adjustments are made for the reference used at the first sensor or references for other sensors in the sheet path, that is, although timing adjustments are carried to downstream sensor references, no adjustments are made to downstream sensors based upon deviations from their own references. Thus, if the initial references are incorrect, the deviations passed down from upstream sensors, may in fact, result in incorrect fault signals at downstream sensors. Merely accumulating deviations from references does not account for the use of references that are inappropriate and inaccurate because of changing machine operating conditions.
Therefore a difficulty in the above prior art device is that the reference for a particular sensor can not be adjusted to account for changes in readings for that particular sensor due to causes such as abnormality of sheet drives and related components, contamination and degradation of the sensor itself. Another difficulty is that the reference for a particular sensor can not be adjusted to account for changes in readings for that particular sensor due to failure of the sensor or inherent manufacturing variations from machine to machine.
It is an object, therefore, of the present invention to provide a new and improved system for setting or adjusting the jam window reference for a sheet tracking sensor. Another object of the present invention is to use actual mean arrival time at critical monitoring stations rather than nominal preset references for setting up or adjusting sheet tracking timing control. Still another object of the present invention is to be able to selectively set sheet tracking timing parameters for a given sensor in response to variable paper path geometries, paper weight, component response, speed variation, and degradation due to aging. Other advantages of the present invention will become apparent as the following description proceeds, and the features characterizing the invention will be pointed out with particularity in the claims annexed to and forming a part of this specification.